A heat wave is an extended time interval of abnormally and uncomfortably hot and unusually humid weather. To be a "heat wave" such a period should last at least one day, but it can last from several days to several weeks.
You can prepare by:
NEVER LEAVE CHILDREN OR PETS IN A PARKED CAR. The temperature can rise to 135 degrees in less than 10 minutes, which can cause death to children or pets.
Please Call 9-1-1 if you see a child or pet left unattended in a parked car
Strenuous activities should be reduced, eliminated, or rescheduled to the coolest time of the day. Individuals at risk should stay in the coolest available place, not necessarily indoors.
Lightweight, light-colored clothing reflects heat and sunlight, and helps your body maintain normal temperatures.
Drink plenty of fluids even if you don't feel thirsty.
Limit over consumption of alcoholic beverages
Spend more time in air-conditioned places. If you cannot afford an air conditioner, spending some time each day (during hot weather) in an air conditioned environment affords some protection.
Don't get too much sun. Sunburn makes the job of heat dissipation much more difficult.